Maintaining the viscosity of solutizer salt solutions



Allg- 1963 s. c; PHENIX, JR, ETAL 3,100,744

MAINTAINING THE VISCOSITY OFSOLUTIZER SALT SOLUTIONS Filed June 2, 19615 SheetsSheet 1 Effect of Xylenols Concentration onViscosity of KOR S mC m m8 w nC 0A GM /AT 1 e s O B /Q l we fi MB M m N mm Wm B m% m% P) BOdm 5 mf ue mm 00 C F O o o o o 0 w m 0 O O O O 7 6 5 4 3 2 1 20 30 1) OXylenols Content in Organic Acids, wt.%

2) A Xylenols Contentin Total Acid Phase //7 venfors Dorr/ss MerchantOwen f? Mi/c/vel/ Bruce C Phen/x, Jz

SUS@IOOF g- 1963 B. c. PHENIX, JR., ETAL 3,100,744

MAINTAINING THE VISCOSITY OF SOLUTIZER SALT SOLUTIONS Filed June 2, 19613 Sheetssheet 2 IOO of Modifier (E BP-400F Cresylotes) has viscosiiy at202 SUS 0 IO 4O I Weight Modifying Acidic Organic Material (SaltSolution) in Highviscosity Cresylote Treating Ag em 7 7f0 5 Dorr/ss H.Merchant Owen E. M/lche/l Bruce CP/Yen/X i/r,

1963 B. c. PHENlX, JR., ETAL 3,100,744

MAINTAINING THE VISCOSITY OF SOLUTIZER SALT SOLUTIONS Filed June 2, 19615 Sheets-Sheet 3 Effect of Different ModifyingAgenls on theViscosiiy andXylenols Content of Aged Cresylole Treating Solution R" 600 e, 500 Mcdifying Agent Symbol l O Cresylofe from E Q 9 Preferred Viscosity 2Cresols ESP-400 F 400 ui Cresolyfe from I 5 Cresols EBP- 403F 3 Phenol OE 300 E fi/ I 7 .2 Z 200 g Preferred 3 Xylenol 5 Concentration Range (7-l5) oo Chorfed Viscosity Equivalent /To Phenol Modifyerin Acid Phose 6,l l

O IO I5 Xylenols (wl.%) in Cresylole Phase in Equilibrium 'lh BE KOHlnven/ors Dar/1'55 H Mere/m Owen R Mllche/l Bruce GP/ven/x, i/n

3,100,744 MAINTAINING THE VISCGSITY F SULUTIZER SALT SOLUTIONS Bruce C.Phenix, Jr., Dorriss H. Merchant, and Gwen R.

Mitchell, Beaumont, Tex., assignors to Soeony Mobil Oil Company, Inc., acorporation or New York Filed June 2, 1961, Ser. No. 114,493 7 fllaims.(Cl. 208-434) The present invention relates to the extraction ofmercaptans from hydrocarbon mixtures with aqueous solutions of alkalimetal hydroxide containing alkali metal salt of at least one solutizerand, more particularly, to the extraction of mercaptans from hydrocarbonmixtures employing 1) the cresylate phase of a mixture of alkali metalhydroxide alkyl phenols (cresols), and water in proportions to produce amixture which at a temperature within the range of about 60 F. and about150 F. separates into a cresylate phase and a heterogeneous hydroxidephase and (2) a two phase or heterogeneous mixture of alkali metalhydroxide, alkyl phenols (ere-- sols), and water in proportions toproduce a mixture which at a temperature within the range of about 60 F.and about 150 F. separates into a cresylate phase and a hydroxide phase.

The use of the aforesaid cresylate phase and the afore' saidheterogeneous mixture as agents for the extraction of mercaptans fromhydrocarbon mixtures is disclosed in the United States Letters PatentNo. 2,850,434, issued September 2, 1958, to Frank W. Brooks, Jr. andClaiborne A. Duval, Jr. These patentees have disclosed that mercaptanscan be removed from hydrocarbon fluids by extraction of the mercaptanswith (l) a cresylate extraction agent consisting essentially of thecresylate phase of a liquid mixture comprising alkali metal hydroxide,cresols extracted from petroleum fractions boiling within the range ofabout 105 F. to about 650 F., and water in proportions to form at atemperature within the range of about 60 F. and about 150 F. a cresylatephase com- United States Patent 0 prising of alkali metal cresylates,alkali metal hydroxide,

and water, and a mutually substantially immiscible hydroxide phasecomprising alkali metal hydroxide and water, or (2) a heterogeneousextraction agent comprising a two phase liquid mixture comprising alkalimetal hydroxide, cresols extracted from petroleum fractions boiling inthe range about 105 F. and about 650 F., and water in proportions toform at a temperature within the range of about 60 to about 150 F. acresylate phase and a mutally substantially immiscible hydroxide phase.These patentees also disclose that mercaptans can be removed fromhydrocarbon fluids by extraction with (3) solutizer salt phaseextracting agent being the solutizer salt phase of a heterogeneous twophase mixture of a solutizer other than the aforesaid cresols, alkalimetal hydroxide and water in proportions to form a solutizer salt phasemutually substantially immiscible with a hydroxide phase at atemperature within the range of about 60 F. to about 150 F., or (4) atwo phase or heterogeneous extraction agent being a mixture of asolutizer other than the aforesaid cresols, alkali metal hydroxide, andwater in proportions to form a solutizer salt 3,100,744 Patented Aug.13, 1963 phase substantially immiscible with a hydroxide phase at atemperature within the range of about 60 and about 150 -F. Thesepatentees disclosedtthat the solutizer salt phase of these latterextraction agents are solid andcan be made fluid by admixing (1)theaforedescribed cresols or (2) alcohols or water soluble ketones inamount to make the solid solutizer salt phase fluid but not misciblewith the hydroxide phase.

In accordance with the method of extracting mercaptans from hydrocarbonfluids described in the aforesaid US. Patent No. 2,850,434, theextraction agent is regenerated by expulsion of the mercaptans andrecycled to the extraction stage. It has now been discovered that whenemploying the extraction agents 1, 2, 3 or 4 briefly describedhereinbefore for the extraction of mercaptans from hydrocarbon fluids,the viscosity of the cresol-containing extraction agent increases withuse until the viscosity of the cresol-containing extraction agent hasincreased to such an extent that operating difliculties, such as theformation of emulsions, the fouling of heat exchangers, valves andpiping, are encountered. These difficulties have required thereplacement of a cresylate phase extraction agent at a cost within therange of $20,000 to $40,000. Thus, a cresylate phase extraction agentcomprising potassium hydroxide, cresols and water initially had aviscosity (SUS at F.) of about 300; after 30 months 'use in extracting27,000,000 barrels of gasoline it had a viscosity (SUS at 100 F.)greater than 700 SUS at 100 F. A similar cresylate extraction agentwhich originally hada viscosity of 280 SUS at 100 F., after treating20,000,000 barrels of gasoline to remove mercaptans had a viscosity of900 SUS at 100 F.

While a cresylate extraction agent which has a viscosity of 700 SUS at100 F. is not inoperative because of the formation of emulsions, andfouling of heat exchangers, valves, and piping, nevertheless forsubstantially trouble-free operation of unit for the extraction ofmercaptans from hydrocarbon fluids with any one of the aforedescribedextraction agents and regeneration of the extraction agent, theviscosity preferably is not greater than about 300 to 400 SUS at 100 F.

It has been found that even when the hydrocarbon fluid from whichmercaptans are to be extracted with one of the aforedescribed extractionagents is first washed with 20 to 30 percent by weight aqueous alkalimetal hydroxide the viscosity of the cresol-containing extraction agentincreases to an intolerable extent. Consequently, the problem of theincreasing viscosity of cresol-containing extraction agents and theconcomitant operating diftficulties requires solution.

It has been found that the increase in the viscosity ofcresol-containing aqueous alkaline extraction agents comprising alkalimetal hydroxide, water and cresols extracted from petroleum fractionsboiling within the range of about F. and about 650 F. is due to aconsiderable extent, if not entirely, to the increase in theconcentration of xylenols in the cresylate phase of the mixture. Thiscorrelation is clearly established by the data presented in Table l andgraphically illustrated in FIGURE I of the drawings. U r

Table I Table II Cresol-containing extraction agent No. 1 2 1 3 4 5Maximum Minimum Com csit'on ercent b Wei ht: 5 Tolerable viscosity SUSat 100 F 700 No limit.

v i ater nff 23. 4 30.3 32.2 36.6 38.7 Preferred viscosity, sUs at 100About 300 to 400-. Do. Potassium hydroxide. 35.0 36.0 37.0 39.0 40.0Usual viscosity of fresh crcsylate bout 350 About 300. Total organicacids L 41. 33. 7 30. 8 24. 4 21. 3 treating agent SUS at 100 1?.Xylenols 17. 0 11.1 7. 9 2. 0 Preferred viscosity for industrial onAbout 300 to 400.- N 0 limit. Distributi nofphenols in total organictimum extraction of megcaptans acids, percent by weight: from gasoline,SUS at 100 F.

Phenol 10.7 34.6 17.5 18.2 100.0 Xylenol concentration in crcsylate Notmore than 15.. Zero. Orcsols. 48. 5 38. 2 56. 7 71. 5 10 phase toproduce preferred viscos- Xylenols 40. 8 27. 2 25. 8 10. 3 ity, weightpercent. Viscosity of extraction agent SUS at V Xylenol concentration incresylate About Do.

100 F .1 722 368 306 202 3 90 phase for industrial optimum extraction ofmercaptans from gasoline, Weight percent. Oresol-containing extractionagent No 1 3 4 15 3 3 346 The foregoing statements apply with equalforce and 23 367 effect to heterogeneous crcsylate treating agents whenthe 402 2 g amount of alkali metal hydroxide solution in the heter- 12223 2 ogeneous mixed treating agent does not exceed that necessary toovercome the small dilution produced by neutrali 65% total organic acidsof extraction agent No. 1 and 35% total organic The data presented inTable I are plotted (1) on the basis of the concentration of thexylenols in the cresols of the total crcsylate phase and (2) on thebasis of the concentration of xylenols in the total crcsylate phases. Itwill be observed that as the concentration of xylenols in the totalcrcsylate phase is reduced from about 17 percent, equivalent to about40.8 percent in the cresols of the crcsylate phase, the viscosity isreduced to about 200 SUS at 100 F. when the concentration of xylenols inthe total crcsylate phase is about 2.5 percent equivalent to 10 percentby weight of the cresols in the crcsylate phase.

In general, a treating agent having a maximum viscosity at 100 F. ofabout 300 to about 400 SUS is preferred. However, a maximum viscosity at100 F. of about 700 SUS (Saybolt Universal seconds) can be tol erated.The minimum viscosity can be as low as local conditions permit. Usually,the viscosity of fresh crcsylate phase treating agent is about 300 toabout 350 SUS ization of the alkali metal hydroxide by the mercaptansextracted from the gasoline.

The aged alkali metal crcsylate phase treating agent can be treated toreduce the viscosity thereof as illustrated by the data presented inTable III and graphically presented in FIGURES 2 and 3. A high viscositypotassium crcsylate phase treating agent having a viscosity at 100 F. of722 SUS Was treated to reduce the viscosity thereof by the addition ofvarious amounts of (A) the potassium salts of cresols having an endboiling point of 400 F., (B) potassium salts of cresols having an endboiling point of 403 F. and (C) by mixing phenol with a mixture of thecrcsylate phase treating agent and sufiicient additional potassiumhydroxide to neutralize the added phenol.

It will be observed that the addition of A (supra) in amount to be 31percent by weight of the modified treating agent reduced the viscosityat 100 F. from'722 SUS to 521 SUS. The addition of B (supra) in theamount to be 52 percent by weight of the modified treating agent reducedthe viscosity at 100 F. from 722 SUS to 441 SUS. The addition of phenol(present as potassium phenate) in the amount to be 35 percent by weightof the modified treating agent reduced the viscosity at 100 F. from722SUS to 368 SUS.

Table III Blend components Blend numbers High viscosity crcsylatetreating agent, percent by weight Oresylate from Gresols EBP of 400 F.,percent by weight Oresylate from Cresols EBP of 403 F.. percent byWeight Oresylate from Phenol} percent by Weight.

1 Treating agent prepared from phenol contains potassium phenate whichis a solid at room temperature.

578 524 ass 0 o -5 50.0 16.3 14.5 11.1

To ensure the formation of a liquid treating agent, the phenol isadmixed with the crcsylate treating agent and the alkali metalhydroxide, for this illustration otassium h droxide do to h blend toproduce a treating agent substantially immiscible with 50 Baume aqueouspotassium hydroxide. p y ad d t e 2 In aqueous crcsylate phase. aCharted viscosity equivalent to phenol modifier in acid phase.

at 100 F. The maximum concentration of xylenols in the crcsylate phaseof a treating agent should not exceed about 15 to 17. percent by weightfor the preferred viscosity of 300 to 400 SUS at 100 F. The foregoing istabulated in Table II.

In FIGURE 2 the viscosities of the various modified treating agents havebeen plotted against the percent by Weight of modifying acidic organicmaterial (salt solution) added to the high viscosity aged crcsylatephase treating agent. It will be observed that phenol as a modifyingagent is more effective than either cresols having an end boiling pointof 400 F. or cresols having an end boiling point of 403 F. It will alsobe observed that the cresols having an end boiling point of 400 F. aremore eifective in reducing the viscosity of the high viscosity cresylatephase treating agent than are the cresols having an end boiling point of403 F.

In FIGURE 3 the viscosities of the modified treating agents have beenplotted against the concentration of xylenols in the total cresylatephase. It will be observed that the curves for the viscosity versus theconcentration of xylenols when the modified treating agent is preparedby the addition of phenol or of cresols having end boiling points of 400F. and 403 F. are substantially parallel.

As has been stated in Table II, the preferred viscosity of the cresylatephase in equilibrium with 50 Baum potassium hydroxide is inthe range ofabout 300 to about 400 SUS at 100 F. Thecu rves FIGURE 3 establish thata viscosity of 300 to 400 SUS at 100 F. is obtained when said cresylatephase contains about 12 percent by weight of xylenols and the balancesubstantially cresols other than xylenols. On the other hand, it hasbeen stated in Table II that the maximum concentration of xylenols forindustrial operation is about 15 percent by weight. It has also been setforth in Table II that a viscosity of 700 SUS at 100 F. can betolerated. The curves in FIGURE 3 clearly show that the optimumconcentration of xylenols, 15 percent by weight, is correlated with acresylate phase viscosity of about 560 to about 600 SUS at 100 F.Accordingly, when the viscosity of the cresylate phase of used treatingagent exceeds 600 SUS at 100 F. and preferably 400 SUS at 100 F., thecresylate phase is diluted with phenols containing a lower concentrationof xylenols than that of the cresylate phase of the used treating agentto reduce the viscosity of the modified, i.e., diluted, cresylate phaseto not more than about 600 SUS at 100 F. and preferably to not more than400 SUS at 100 F. while maintaining the xylenol concentration in thecresylate phase of the modified treating agent in the range of about topercent by weight and preferably in the range 7 to 15 percent by weightand the balance substantially phenols other than xylenols. The modifiedtreating agent then has a cresylate phase comprising not more than 15percent by weight and not less than about 7 percent by weight andpreferably about 10 to about 15 percent by weight xylenols balance tomake 100 percent of the cresylate phase substantially phenols. (Thephrase cresylate phase has been used herein-before and is usedhereinafter to designate (1) the cresylate phase of a heterogeneoustreating agent comprising alkali metal hydroxide, phenols, and water inthe proportion that at a temperature in the range of about 60 F. toabout 150 F. separates into a cresylate phase and a hydroxide phase, (2)the homogeneous treating agent comprising the cresylate phase only ofthe aforesaid 1) heterogeneous treating agent, (3) the sol-utizer saltphase of a heterogeneous treating agent comprising a mixture of alkalimetal salts of at least one solutizer other than cresols, alkali metalhydroxide, and water in proportions that at a temperature in the rangeof about 60 F. to about 150 F. separates into a solutizer salt phase anda hydroxide phase and containing an amount of alkali metal salt ofcresols to maintain the aforesaid solutizer salt phase liquid in therange of about 60 F. to about 150 F, and (4) the homogeneous treatingagent comprising the solutizer salt phase only of the aforesaid (3)heterogeneous treating agent.) The concentration of xylenols is thepercent by weight of that phenol in the mixture not of the theoreticalalkali metal salt of that phenol.

Accordingly, the present invention provides in a cycle manner preparinga fresh treating agent comprising alkali metal hydroxide, alkali metalsalt of phenols including xylenols, and water which at a temperature inthe range of about 60 F. and about 150 F. separates into a cresylatephase and a hydroxide phase, said cresylate phase containing not morethan 15 percent by weight and not less than about 7 percent by weight ofxylenols and when in equilibrium with 50 Baum aqueous alkali metalhydroxide said cresylate phase has a viscosity in the range of about 300to about 400 SUS at F., extracting mercaptans from hydrocarbon mixtureswith (1) the aforesaid cresylate phase and the aforesaid hydroxide phaseor (2) with the aforesaid cresylate phase only to obtain fouled treatingagent, regenerating said fouled treating agent by steam distillation,fortifyin-g said cresylate phase with respect to the concentration ofalkali metal hydroxide, extracting mercaptans from hydrocarbon mixtureswith the said regenerated and fortified aged treating agent until whenthe cresylate phase of said treating agent is in equilibrium with 5 0Baum aqueous alkali metal hydroxide the viscosity of said cresylatephase exceeds 700 SUS at 100 F., preferably When the SUS at 100 F..exceeds 600, diluting the cresylate phase with phenols having aconcentration of xylenols less than that of the aforesaid aged treatingagent and preferably less than 7 percent by weight including phenolssubstantially devoid of xylenols, to provide a modified treating agentthe cresylate phase of which has a viscosity at 100 F. not greater than600 SUS and preferably not greater than 400 SUS and contains not morethan 15 percent by weight of xylenols and preferably about 10 to about15 percent by weight xylenols the balance to make 100 percent by weightof the organic material neutralizable with alkali metal hydroxide beingphenols other than xylenols boiling below about 650 F., and extractingmercaptans from hydrocarbon mixtures with the aforesaid modifiedtreating agent whilst maintaining the viscosity at 100 F. not greaterthan 600 SUS and the xylenol concentration not greater than 15 percentby weight but not less than about 7 percent by weight of theneutralizable organic material in the regenerated, fortified treatingagent.

For illustrative purposes the following characteristics of the cresylatephase of a treating agent comprising phenols, potassium hydroxide, andwater are given in Table IV.

We claim:

1. In the treatment of hydrocarbon mixtures containing mercaptanswherein a hydrocarbon mixture containing mercaptans is contacted with atreating agent having the capabilities of extracting mercaptans andcomprising a cresylate phase havinga viscosity at 100 F. of about 300 toabout 400 SUS to obtain a fouled treating agent, regenerating saidcresylate phase by steam distillation, and extracting mercaptans fromhydrocarbon mixture, and wherein the viscosity at 100 F. of saidcresylate phase after aging by use increases to greater than about 700SUS at 100 F. and the xylenol concentration in the neutralizable organicmaterial in the aged cresylate phase increases to more than 15 percentby weight, the improvement which comprises diluting said cresylate phasewith at least one phenol having a concentration of xylenols less thanthat of the aforesaid aged cresylate phase to provide a modifiedtreating agent the cresylate phase of which has a viscosity at 100 P.not greater than about 600 SUS when in equilibrium with 50 Baum alkalimetal hydroxide and a xylenol content not in excess of 15 percent byweight of the neutralizable organic material.

2. The method set forth in claim 1 wherein the viscosity 7 of thecresylate phase is reduced to not more than about 500 SUS at 100 F.

3. The method set forth in claim 1 wherein the viscosity of thecresylate phase is reduced to not more than 400 SUS at 100 -F.

4. The method set forth in claim 1 wherein the viscosity of thecresylate phase is reduced to not more than about 600 SUS at 100 F. andthe concentration of xylenols to in the range of about 7 to about 15percent by weight of the neutralizable organic material in saidcresylate phase.

5. The method set forth in claim 1 wherein the viscosity of thecresylate phase is reduced to not more than about 600 SUS at 100 F. bydilution with cresols having an end boiling point not higher than about400 F.

6. The method set forth in claim 1 wherein the viscosity of thecresylate phase is reduced to not more than about 600 SUS at 100 F. bydilution with a mixture of 8 cresols having an end boiling point nothigher than about 403 F.

7. In the treatment of mercaptan-containing hydrocarbon mixtures toextract mercaptans therefrom using as extracting medium an agentcomprising cresylate, alkali metal hydroxide, and water, said agent alsocontaining xylenols, and wherein the viscosity of the agent increaseswith use'to a value greater than 700 SUS at 100 F., the improvementcomprising decreasing the viscosity of the agent to less than 700 SUS at100 F., by adding to the agent a diluent comprising phenols having axylenol con tent less than that of said agent.

References Cited in the file of this patent UNITED STATES PATENTS DuvalSept. 12,.19 61

1. IN THE TREATMENT OF HYDROCARBON MIXTURES CONTAINING MERCAPTANSWHEREIN A HYDROCARBON MIXTURE CONTAINING MERCAPTANS IS CONTACTED WITH ATREATING AGENT HAVING THE CAPABILITIES OF EXTRACTING MERCAPTANS ANDCOMPRISING A CRESYLATE PHASE HAVING A VISCOSITY AT 100*F. OF ABOUT 300TO ABOUT 400 SUS TO OBTAIN A FOULED TREATING AGENT, REGENERATING SAIDCRESYLATE PHASE BY STEAM DISTILLATION, AND EXTRACTING MERCAPTANS FROMHYDROCARBON MIXTURE, AND WHEREIN THE VISCOSITY AT 100*F. OF SAIDCRESYLATE PHASE AFTER AGING BY USE INCREASES TO GREATER THAN ABOUT 700SUS AT 100*F. AND THE XYENOL CONCENTRATION IN THE NEUTRALIZABLE ORGANICMATERIAL IN THE AGED CRESYLATE PHASE INCREASES TO MORE THAN 15 PERCENTBY WEIGHT, THE IMPROVEMENT WHICH COMPRISES DILUTING SAID CRESYLATE PHASEWITH